Field
Various example embodiments relate to a pen input device having a malfunction prevention function and a method of preventing a malfunction thereof.
Description of Related Art
Nowadays, portable electronic devices provide an input and output function using a touch screen for convenience of an input and a slim trend, and for this purpose, the touch screen includes a display panel and a touch panel.
In order to provide an elaborate touch input as well as recognition of a hand touch, a mobile terminal having a touch screen supports a touch input device such as a stylus or an electronic pen. Touch technology using such a stylus pen is largely classified into an active type requiring power and a non-powered passive type, and when an electromagnetic field occurring in a digitizer pad closely meets with a metal coil attached to an end portion of a pen, an electromagnetic induction phenomenon occurs and thus a change occurs in the already formed electromagnetic field and thus the pen detects and operates the change.
The active electronic pen includes a power source such as a battery. That is, the active electronic pen drives an LC resonant circuit formed with an inductor L and a capacitor C through the power source. In this case, the mobile terminal receives a wireless signal occurring in the LC resonant circuit of the electronic pen with an array form of antenna therein and recognizes a location of the electronic pen using reception strength of each antenna.
The passive electronic pen does not include a separate power source and receives and operates power from a mobile terminal using an electromagnetic induction phenomenon. For example, the passive electronic pen using an electromagnetic induction phenomenon generally uses an electromagnetic resonant (EMR) method using an LC resonant circuit. Such an EMR method of passive electronic pen using the LC resonant circuit receives a wireless signal from the mobile terminal through the LC resonant circuit and transmits a reflection signal of the received wireless signal to the mobile terminal. In this case, the mobile terminal receives the reflection signal transmitted from the LC resonant circuit of the electronic pen with an array form of antenna therein, measures reception strength of each antenna, and recognizes a location of the electronic pen.
An EMR method of electronic pen using the LC resonant circuit provides state information such as a pen pressure and a button input through a resonant frequency change of the reflection signal. For this purpose, a conventional EMR method of electronic pen using an LC resonant circuit may include a capacitor, inductor, variable inductor, and variable capacitor for changing a resonant frequency of the LC resonant circuit according to a pen pressure or a button input.
In this way, when a conventional stylus pen approaches a touch screen, the conventional stylus pen starts to recognize this, and when the conventional stylus pen touches the screen, the screen recognizes a pen pressure and writing is performed on the screen.
However, in a state in which a pen is placed on the screen, for example, in a state in which a pen is not used, even when the pen is laterally shaken or even when the pen and the screen are horizontally disposed such that the pen almost touches with the screen, it is recognized that the pen is used and thus a pen point occurs in an intermediate portion instead of an end portion of the pen and thus there is a problem that writing malfunctions.